Liquid air refrigerator



Filed Dec. 7, 1945 6 v H Mk n, l

Aug. 23, 1949. T, w. RosEBAUGH 2,479,866

I LIQUID AIR REFRIGERATOR Filed Dec. '7, 1945 2 Shets-Sheet 2 v l W ZO/\O Patented Aug. 23, 1949 UNITED STATES ,PATENTYOFFICE i LIQUID AIRREFRIGERATOR Theodore W. 4Ros'ebaugh, `Oakland, Calif., allsignor toShell Development Company, San Francisco, Calif., a corporation ofDelaware Application December 7, 1945, Serial No. 633,362

(ol. s2- 92) 6 Claims.

This invention relates to the cooling orrefrigeration of foodstuffs bymeans ofl liquid air and is particularly concerned with the safe andeconomical preservation of foodstuffs during storage.

The invention is primarily concerned with keeping fresh foodstuffs at asuillciently low temperature sothat 'deterioration of the foodstuffs isprevented.l

It is an object of this invention to provide new and useful apparatusfor the refrigeration of foodstuffsusing expendable liquefied gas ormixture of liquefied gases.

It is another object of this invention to provide a new and usefulrefrigeration system which may be adopted for household use.

AIt is another object of this invention to provide a new and usefulapparatus by which the deep freezing of foodstuffs as well as the normalrefrigeration of foodstuffs may be accomplished in the home.

It is a further object of this invention to provide an apparatus usingliquefied air as an expendable refrigerant.

By the term liquid air" I include all liquefied mixtures of oxygen andnitrogen. In other words I include liquid air consisting of oxygen andnitrogen in the proportions they occur in nature as well as liquid airproduced as a byproduct of industrial processes wherein'the proportionsof oxygen and nitrogen may vary considerably from the proportionsoccurring in nature.

The further advantages and objects of my invention will be apparent fromthe following description of a household refrigerator utilizing theinvention.

Referring to the accompanying drawings:`

Figure I is a front elevation (with part of door removed) of a.household refrigerator employing liquid air as the refrigerant.

Figure II is a plan view of a household refrigerator taken along lineII-II of Figure I.

Figure III is a vertical section of a household refrigerator taker alongthe line III-III of Figure I.

Figure IV is an end elevation of an alternate construction of the lowerportion'of the refrigerator.l

4Figure V is an enlarged cross sectional view of the gas conduit shownin Figure I, It and III.

Referring to Figure I, II and III numeral I represents generally aninsulated refrigerator cabinet provided with the usual hinged door 2 inthe front face. The door 2 is of course also insulated. In the lowersection of the refrigerator,

2 shelves 3 are provided for the placement of the various food items itis desired to cool or preserve'.

In the upper part of the refrigerator there is located a sheet metal lowtemperature compartment 4 having an insulated lid or lhatch cover 5 sothat access to this compartment is obtained without opening the door 2.

Slidably mounted on a plate 8 located in the cabinet below the lowtemperature compartment 4 are several trays 'I for the making' of icecubes. Recessed in the inner back panel 8 of the refrigerator and on theinner side of the insulation 8 is a vertical duet I 0 which may be ofcomposite construction as will be explained hereinafter. The duct I0terminates at its upper end near the top of the low temperturecompartment 4 and extends downward and is connected at its lower end toa Dewar flask Il mounted in thecabinet underneath the refrigeratorcompartment. This Dewar flask II is of usual construction having aninner shell and an outer shell. The Dewar flask is provided with a fillspout I2 which extends to the front of the cabinet and is provided witha snap lid I3 at its outer end.

Depending into the Dewar ilask II to close to its bottom is a copper orother metal plate Il which leads upward to form one side of the neck I5of Dewar flask and extending further forms the front face I6 of the ductl0.

Copper fins I1 are attached to the outer side of the front face I6 ofthe duct. Located under the ice trays 1 near the back of therefrigeration space is a small electric fan I8 provided with anadjustable thermostat I9 connected in series with the fan and a sourceof electric power. The electric fan I8 is arranged so that whenoperating it will cause air to ilow toward the ns I'I.

A director ring 20 surrounds the electric fan I8 to increase itseiiiciency and serves also to shield the fan from possible damage.

The operation of my refrigeration system is as follows:

The Dewar flask II is lled with liquid air 2| from an outside sourcethrough the ll spout l2. This liquid air is at a temperature of about315 F. varying slightly upon its composition.

The heat gained through the walls of the Dewar flask is comparativelysmall owing to the eiective insulation inherent from the construction. f

However some heat is transmitted to the liquid air by the copper plateI4 which dips into the liquid air.

This copper plate due to the high heat conductivity of the metal drawsheat from its upper section, which as will be noted from the drawings,forms the front face I6 of the duct I0.

The copper plate in turn draws heat from the contents of therefrigeratorl compartment through the contact of the air in therefrigerator with the copper plate and the fins I1 attached to it.

The heat thus transmitted from the refrigerator compartment to theliquid air in the Dewar flask II causes ebullition of some liquid air.

This vaporized liquid air (at considerably below F.) passes upwardthrough the duct Ill withdrawing more heat from the walls of the duct.

As will be apparent to those skilled in the art, the emciency of thesystem will be somewhat improved if the side and back walls of the ductIII are made of non-metallic material, such as for example, an asbestoscement composition. This detail may be more clearly seen by referring toFigure V wherein numeral 22 represents nonmetallic duct material.

'I'he cold vaporized liquid air after absorbing heat by heat exchangewith the interior of the refrigerator in its upward journey iseventually discharged from the upper end of the duct into the lowtemperature compartment 4.

The cold air still considerably below 32 F. flows downward (owing toitsdensity being greater than the existing air in the refrigerator) overany articles of food in the low temperature compartment.

The cold air then ows out through the bottom of low temperaturecompartment through openings 23 and then ilows across and around the icetrays 7.

The cold air eventually flows through openings 2d in the rear of theplate 6 into the lower or normal refrigeration section. The path of flowof cold air as above described can be readily seen from an examinationof Figure III ofthe drawings wherein arrows indicate the ow.

As should be realized the copper fins I'I and the copper plate I6forming one wall of the duct I0 and also serving as the heat transfermeans for conveying sumcient heat to the liquid air 2I inthe Dewar flaskIi will soon become coated with a layer of ice due to the freezingthereon of the water vapor in the normal air of the refrigerator. Thislayer of ice will reduce the refrigeration effect and serve as a partialinsulator. Therefore if further refrigeration is required, a removal orpartial removal of some of the ice coating should be effected. For thispurpose the electric fan I8 is provided. Upon a desired temperature inthe compartment being exceeded the fan motor starts up due to thethermostat control I9 and by causing a more rapid movement of air acrossthe surface of ins I l and copper plate I6 improves the heat transferand effects a further lowering of the temperature of the air in therefrigerator compartment (and in turn of its contents). As air is beingsupplied to the interior of the refrigerator it is necessary that someprovision be made for the escape of air from the compartment. For thispurpose air off-take pipes 25 are provided.

In Figure IV I have shown an alternate construction for the lower partof the refrigerator. Referring to this Figure IV it will be noted thatthe Dewar flask Il is not sepaarted by insulation 9 from the interior ofthe refrigerator, but is enclosed within the insulation surrounding therefrigerator compartment. By this construction any Aheat gain throughthe walls of the Dewar flask II will be heat removed from the contentsof the refrigerator compartment.

While in the above description of my preferred refrigerator I have showna specific construction, it should be understood that I contemplate thatvariations and changes can be made to meet particular situations.

For example, where there is not a readily available souree of power toprovide an increase in circulation of air across the copperplate I6other means of increasing the degree or rate of refrigeration may beemployed.

Although I have shown my refrigeration system as applied to arefrigeration cabinet containing both a low temperature section andnormal refrigeration section, it will be apparent that the system may beused in a cabinet provided solely with a low temperature section orsolely with a normal refrigeration section.

Furthermore while the unit described is specically arranged forhousehold use, it is contemplated it could be utilized for therefrigeration of' larger insulated compartments such as cold storagewarehouses, meat packing plants and the like.

The system moreover could be applied to transportation of foodstuffs inmobile units such as by railroad refrigerator cars, by motor trucks orby air transport.

In application to such units the Dewar ask could be located Within therefrigerator compartment so as to insulate it from the outside heat.

If desired, where the system is applied to air transportation, some ofthe vaporized liquid air supply could be diverted by suitable piping forthe use of the occupants of the plane when fiying at high altitudes.

I further fully appreciate that where desired liquid air could be forcedin its liquid state into the refrigeration compartment by the use of aneduction pipe and the creation of a slight pressure upon the surface ofthe liquid air in the Dewar flask, or by other means.

I claim as my invention:

1. Apparatus for using liquid air as a refrigerant comprising a heatinsulated refrigeration compartment, a highly insulated container forliquid air, a high heat conductor located in said compartment andextending into said liquid air container, and a vapor duct from saidliquid air container passing in heat exchange with the wall of saidrefrigerator compartment along a substantial portion of the lengththereof and terminating in the interior of said refrigeratorcompartment. Y

2. Apparatus for using liquid air as a refrigerant comprising a heatinsulated refrigeration compartment, a heat insulated container forliquid air, a heat conductive metallic plate located in said compartmentand extending into said liquid air container, air guiding means for'leading air from the vapor space of said liquid air containerterminating in the interior of the refrigerator compartment, and athermostatically controlled electric fan in said refrigeratorcompartment disposed to' circulate air along said heat conductivemetallic plate.

3; Apparatus for using liquid air as a refrigerant comprising a heatinsulated refrigeration compartment, a heat insulated container forliquid air, a heat conductive metallic plate located in sad compartmentand extending into said liquid air container, air guiding means forleading air from the vapor space of said liquid air container disposedto conduct vapors in heat eX= 5 change with said heat conductingmetallic plate and opening to the interior of the refrigeratorcompartment, and a thermostatically controlled electric fan in saidrefrigerator compartment disposed to circulate air along said heatconductive metallic plate.

4. Apparatus or using liquid air as a refrigerant comprising a heatinsulated refrigeration compartment, a heat insulated container forliquid aix', a heat conductive metallic plate located in saidcompartment and extending into said liquid air container, expanded meta]surfaces on said heat conductive metallic plate within said compartment,a duct from the vapor space of said liquid air container opening to theinterior of said refrigerator compartment, at least a portion of thewall of said duct being formed -by said heat conductive metallic plate,and a thermostatically controlled electric fan in said refrigeratorcompartment disposed to circulate air along said exgn audacesub-compartment and extending into said liquid air container, airguiding means for leading air from the vapor space of said liquid aircontainer passing in heat exchange with the wall of said warmersub-compartmentv along a substantial portion of the length thereof andopening to the interior of said low temperature sub-compartment, apassageway between said low temperature sub-compartment and said warmersub- 10 compartment, and a thermostatically controlled 15 said heatconductive metallic plate forms at least a portion of the wall of saidduct.

THEODORE W. ROSEBAUGH.

REFERENCES crrEn The following references are oi! record in the ille ofthis patent: 4

UNITED STATES PATENTS u Number Name Date 1,719,692 Des Jardins July 2.1929 2,346,837 Grooms Apr. 1.8. 1944

